title: The effect of insulin feedback on closed loop glucose control.
abstract: BACKGROUND
  Initial studies of closed-loop proportional integral derivative control in individuals with type 1 diabetes showed good overnight performance, but with breakfast meal being the hardest to control and requiring supplemental carbohydrate to prevent hypoglycemia.
  
  
  OBJECTIVE
  The aim of this study was to assess the ability of insulin feedback to improve the breakfast-meal profile.
  
  
  METHODS
  We performed a single center study with closed-loop control over approximately 30 h at an inpatient clinical research facility.
  
  
  METHODS
  Eight adult subjects with previously diagnosed type 1 diabetes participated.
  
  
  METHODS
  Subjects received closed-loop insulin delivery with supplemental carbohydrate as needed.
  
  
  METHODS
  Outcome measures were plasma insulin concentration, model-predicted plasma insulin concentration, 2-h postprandial and 3- to 4-h glucose rate-of-change following breakfast after 1 d of closed-loop control, and the need for supplemental carbohydrate in response to nadir hypoglycemia.
  
  
  RESULTS
  Plasma insulin levels during closed loop were well correlated with model predictions (R = 0.86). Fasting glucose after 1 d of closed loop was not different from nighttime target (118 ± 9 vs. 110 mg/dl; P = 0.38). Two-hour postbreakfast glucose was 132 ± 16 mg/dl with stable values 3-4 h after the meal (0.03792 ± 0.0884 mg/dl · min, not different from 0; P = 0.68) and at target (97 ± 6 mg/dl, not different from 90; P = 0.28). Three subjects required supplemental carbohydrates after breakfast on d 2 of closed loop.
  
  
  CONCLUSIONS
  Insulin feedback can be implemented using a model estimate of concentration. Proportional integral derivative control with insulin feedback can achieve a desired breakfast response but still requires supplemental carbohydrate to be delivered in some instances. Studies assessing more optimal control configurations and safeguards need to be conducted.
authors.affiliation: Children's Hospital Boston, 300 Longwood Avenue, Boston, Massachusetts 02115, USA. garry.steil@childrens.harvard.edu
authors.forename: Garry M
authors.initials: GM
authors.lastname: Steil
authors.forename: Cesar C
authors.initials: CC
authors.lastname: Palerm
authors.forename: Natalie
authors.initials: N
authors.lastname: Kurtz
authors.forename: Gayane
authors.initials: G
authors.lastname: Voskanyan
authors.forename: Anirban
authors.initials: A
authors.lastname: Roy
authors.forename: Sachiko
authors.initials: S
authors.lastname: Paz
authors.forename: Fouad R
authors.initials: FR
authors.lastname: Kandeel
mesh_terms: D000328:Adult; D000465:Algorithms; D015374:Biosensing Techniques; D001786:Blood Glucose / Q000378:metabolism*; D002138:Calibration; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy*; D004040:Dietary Carbohydrates / Q000627:therapeutic use; D025461:Feedback, Physiological / Q000502:physiology*; D005260:Female; D006801:Humans; D007003:Hypoglycemia / Q000188:drug therapy; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D007328:Insulin / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D019518:Postprandial Period / Q000502:physiology; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007004:Hypoglycemic Agents; D007328:Insulin